A Washington, D.C., watchdog group today called for a federal investigation into Republican presidential candidate Newt Gingrich and what the group called potentially illegal lobbying activities connected to a 2003 healthcare bill.

The non-profit group Citizens for Responsibility and Ethics in Washington (CREW) filed a complaint with the U.S. attorney in D.C. and the FBI in which it claims Gingrich repeatedly met with or called members of Congress to pressure them to pass a contentious 2003 Medicare reform bill -- legislation from which members of a Gingrich-founded group may have directly profited and Gingrich himself may have indirectly benefitted.

CREW requested prosecutors and the FBI investigate whether Gingrich's efforts to get the bill passed amounted to lobbying and, if so, whether Gingrich broke the law by failing to register as a paid lobbyist.

R.C. Hammond, a representative of Gingrich's presidential campaign, did not immediately respond to a request for comment for this report, but last month Gingrich responded to previous accusations about the healthcare bill.

"I'm allowed as a citizen to say I'd like to see this passed and that's not lobbying," he said, according to CNN. "I wasn't paid by anybody to say that. It was a public position I had taken for a practical reason ... That was a public position taken publicly and is literally by definition not lobbying."

Complaint: 'Financial Motive' Behind Gingrich's Push

The new CREW complaint centers around The Center for Health Transformation (CHT), a paid membership group aimed at creating "better health and more choices at lower cost," created by Newt Gingrich's consulting company, Gingrich Group. CHT's earliest members included at least three companies who dealt directly in the healthcare industry, CREW said.

The same year CHT was created, debate raged in Congress over a new Medicare bill. During the debate, Gingrich went to work "directly contact[ing] members of Congress and the administration to lobby for the inclusion of specific provisions in the legislation," CREW said. Citing CHT newsletters, CREW claimed that in addition to calls and individual meetings, CHT sponsored a health care briefing between Gingrich and congressional staff and included Gingrich's reports on progress on the bill in their membership newsletters. Gingrich was in "regular communication with the White House and key players on Capitol Hill" about the bill, CHT reportedly said on their website.

Last month, CNN reported former Republican Congresswoman from Colorado Marilyn Musgrave came forward to say she was one of the officials called by Gingrich during the debate.

"Newt called me to vote yes," Musgrave reportedly said. Musgrave said she had already made up her mind, however, and voted against the bill. Two other Republicans, current Rep. Jeff Flake and former congressman Butch Otter, told the Des Moines Register in December they too had been urged by Gingrich to vote for the bill.

"He told us, 'If you can't pass this bill, you don't deserve to govern as Republicans,'" said Flake. "If that's not lobbying, I don't know what is."

According to the CREW complaint, when the bill passed in December 2003, Gingrich brought high-paying members of CHT to the bill signing and CHT later bragged in a newsletter it had "worked with the Bush administration, key leaders in the House and Senate, AARP and key experts to develop and help pass a transformational Medicare Bill."

"Mr. Gingrich, CHT, and CHT's members had a variety of financial motives for lobbying to pass the bill," CREW says in the complaint. "As for Mr. Gingrich, helping pass the bill and taking credit for that could have -- and apparently did -- result in more companies joining CHT and paying its hefty membership fees. Separately, several CHT members, particularly those involved in drug manufacturing and electronic healthcare records, stood to benefit financially" from parts of the bill.

CREW said Gingrich appeared to be lobbying government officials on behalf of CHT and did not disclose it. Therefore, both Gingrich and CHT should be investigated for potentially violating the Lobbying Disclosure Act of 1995, the group said.

Gingrich: 'No Lobbying of Any Kind'

In addition to Gingrich's denial, documents available on the CHT website say that the group does "absolutely no lobbying."

But CREW Executive Director Melanie Sloan said that Gingrich claiming that he was merely expressing an opinion and the CHT claiming no lobbying went on are not enough when private meetings and phone calls with government officials are involved.

"Despite his repeated disavowals, the evidence shows Mr. Gingrich was lobbying on the Medicare reform bill," Sloan said. "The idea that Mr. Gingrich was acting as a civic-minded private citizen when he was lobbying for the Medicare bill is ludicrous."

Before the latest accusations, Gingrich had previously spoken out against allegations he served as a lobbyist for the troubled mortgage corporation Freddie Mac under the guise of the Gingrich Group.

"We said flatly from day one we will do no lobbying of any kind, and I will not take any client who has a position I don't agree with," Gingrich said in November of the Freddie Mac accusations.